1. Field of the Invention
The present invention relates to a thermochromic substrate and a method of manufacturing the same, and more particularly, to a thermochromic substrate and a method of manufacturing the same, in which the crystallinity of a thermochromic layer can be improved.
2. Description of Related Art
Thermochromism refers to the phenomenon in which an oxide or a sulfide of a transition metal undergoes a change in its crystal structure below and above a specific temperature (i.e. transition temperature (Tc)), so that its physical properties (electrical conductivity and infrared (IR) transmittance) suddenly change.
When a glass is coated with a thin film that has such thermochromic capability, a “smart window” can be produced, which transmits visible light but blocks near infrared rays and infrared rays at a predetermined temperature or more in order to prevent the indoor temperature from increasing. The application of smart glass to windows of vehicles or buildings may be very effective in saving energy. Materials that exhibit thermochromism include oxides of several transition metals, of which vanadium dioxide (VO2) is being studied since its transition temperature is 68° C., which is relatively close to a temperature that is practically applicable.
Accordingly, in order to manufacture vanadium oxides, which are present in a variety of crystalline phases, such as V2O3, V3O5, V4O7, V5O9, V6O11, V6O13, V4O9, V3O7, V2O5 and VO2, into a crystalline phase of VO2, a method of heating a glass substrate to a high temperature and then coating the glass substrate with a vanadium oxide, a method of coating a glass substrate with a vanadium oxide, followed by post annealing, and the like are used.
However, these methods have a problem in that, when a sodalime glass, which is generally used as a glass substrate, is coated with a vanadium oxide, the vanadium oxide would also be amorphous due to the amorphousness of the glass.
There is also a problem in that sodium (Na) ions inside the sodalime glass diffuse into the thermochromic layer at temperatures of 350° C. or higher, thereby degrading the characteristics of the thermochromic layer.
Accordingly, in the related art, an oxide- or nitride-based thin film is added between the glass substrate and the thermochromic layer. In this case, however, the substances that form the thermochromic layer are different from those that form the thin film, thereby degrading the crystallinity of the thermochromic layer. In addition, the process of forming the thermochromic layer becomes difficult.
The information disclosed in this Background of the Invention section is only for the enhancement of understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.